Telephone transmission system.



W. A. FRICKE.

TELEPHONE TRANSMISSION SYSTEM.

APPLICATION FILED MAR. 17. 1913.

1,209,27Q Patent-ed Dec 19,1916.

TT'OR/VEYJ s'rnrns new orr WILLIAM A. FRICKE, OF CHICAGO, ILLINOIS,ASSIGNOR TO AUTOMATIC IEILE(,ICIIEtIC COMPANY, OF CHICAGO, ILLINOIS, ACORPORATION OF ILLINOIS.

TELEPHONE TRANSMISSION SYSTEM.

Application filed March 17, 1918.

To all whom it may concern Be it known that I, WILLIAM A. FRICKE, acitizen of the United States of America, and resident of Chicago, Cookcounty, Illinois, have invented a certain new and useful Improvement inTelephone Transmis-- sion Systems, of which the following is aspecification.

My invention relates to telephone systems, and more particularly to asystem adapted for railroad despatch work in which a plurality ofstations isassociated with a single line.

One of the objects of my invention is to provide an improved arrangementof the substation circuits whereby a conversation may be carried onbetween two subscribers in a very eflicient manner.

Basis connected to one side of the line through A further featurecomprises the provision of means for providing a path for incoming.voice currents as well as'forout going voice currents, and means forpreventing the outgoing voice currents being shunted through" thereceiver of the calling station.

These and other features of my invention will be more readily understoodby reference to the accompanying drawing, which representsdiagrammatically a telephone line with three subscribers stationsbridged across the same.

In accordance with my invention, each substation on the line is bridgedacross the line wires. One side of the station circuit a condenser,whereas the other side'of the station is connected to the other side ofthe line through a contact controlled at the switch hook, which contactis normally open. Between these two points there is located thesubstation equipment, which is divided into two branches, one branchcontaining a receiver and the other branch containing the secondarywinding of the induction coil. In series with the primary winding in alocal circuit there is contained a transmitter and a battery forenergizing the same. The said induction coil is provided with a tertiarywinding, which winding is at times adapted to be included in a localcircuit with the receiver, during which times the receiver is completelydisconnected from direct connection with the line wires. Associated withone of the stations, of-which one may be considered a train despatchersSpecification of Letters Patent.

Serial No. 754,853.

station, there is provided a suitable impulsetransmitting device foroperating the signals at the other stations on the line and inconnectlon with said other stations there is provided a deviceresponsive to said impulse transmitter for controlling the signal at thestatlon with which it is associated. Such lmpulse-sending andimpulse-receiving devices are well known and form no feature of mypresent invention.

In the accompanying drawing there are shown the line wires A and Bacross which the several stations C, D, E, etc., are bridged. At F(station 0) there is indicated the sigr al-transmitting device foroperating the signal-recelving instruments G and H, etc, at the otherstations. All other apparatus at the station G besides the signalingdevice F is the same as all other apparatus at the other stations,except the signal-receiving device, so that a description of one of thesubstations will suflice for all. It will be observed that theconnection between the station apparatus and the line B is controlled bythe switch hook 2 through the contacts 3 and 4. The connection to theother side of the line, it will be seen, is completed through thecondenser 5. Normallythat is, when the apparatus is not in use-the-Patented Dec. 19, 191%.

the non-inductive resistance 9 on one side, a

and through the springs 10 and 11 with the spring 3 controlled by theswitch hook on the other side. It will therefore be seen that if thereceiver is removed from the hook a circuit is established through thestation C from the conductor A, through the condenser 5, non-inductiveresistance 9, springs 7 and 8, receiver 6, springs 10 and 11 and throughthe springs 3 and 4 to the other side of. the line B. This is thecondition of the apparatus when the instrument is in con dition forlistening.

In order to put the instrument in condition for talking that is, fortransmitting voice currents to the lines A and B-a button 12 is pressed,with the result that the circuit is opened at the springs 7 and 8 andalso at the springs 10 and 11, thus disconnecting the receiver 6completely from both sides of the line. However, a new circuit is closedthrough the instrument from the line wire A, through the condenser 5 andthe secondary winding 13 of the induction coil,

through the springs 14 and 11 to the other side of the line by theclosure of Contact between the springs 11 and 1 1 as a result of thepressing of the button. It will be observed that at the same time thisnew circuit is closed the receiver 6, which was disconnected from acrossthe line conductors A and B, is

thrown into a local circuit including the tertiary winding 14 by theclosure of connection between the springs 8 and 15. It will be observedfurther that at the same time the energizing circuit through the primarywinding 16 is established by the closure of connection between thesprings 17 and 18. Under this new condition voice currents may betransmitted to the line for affecting the receivers at the otherstations. Although the receiver has been disconnected from the otherbranch to prevent the shunting of the talking currents therethrough, ithas been inductively connected with the line in thenew local circuit.This permits anyone who has been talking to listen and determine if theparty to whom he is talking is himself talking, without seriouslyaffecting the transmission over the line.

The resistance 9, which is in series with the receiver, offerssufficient impedance to voice currents so that if one or more receiversare left down at the substations, thereby placing one or more shuntsacross the line, these shunts will have sufficient resistance to preventthese shunts rendering the telephone line inoperative.

\Vhile I have illustrated and described one particular embodiment of myinvention, it is to be understood, of course, that I do not limit myselfto the particular construction shown and described.

\Vhat I claim as my invention is 1. In a telephone system, a metallicline circuit, a bridge across said circuit, said bridge including a pairof branches, a winding of an induction coil connected with one of saidbranches, a telephone transmitter in a local circuit inductivelyassociated with said winding, a receiver connected in the other branch,a switch for disconnecting said receiver from the path of voice currentspassing through said winding, a tertiary winding for said inductioncoil, and means for including said tertiary winding in series with saidreceiver.

2. In a telephone system, a metallic line circuit, a bridge across saidline circuit, said bridge including a condenser and a hook switch, apair of parallel connections between said condenser and switch," one ofsaid par l el connections including a winding of an induction coil, atransmitter in a local circuit inductively associated with said winding,a receiver in the other branch, and a switch normally maintaining thebranch through said receiver closed and the branch through the windingof the induction coil open, said switch adapted when operated to openthe normally closed branch and close the normally open branch, wherebysaid receiver is removed from the path of voice currents passing throughsaid winding, a tertiary winding for said induction coil, normally openconnections from said tertiary winding to said receiver, and a switchfor closing said normally open connection.

3: In a telephone system, a metallic line circuit, a bridge across saidcircuit, said bridge including a condenser and a pair of parallel branchconnections, a"transmitter operatively associated with one of saidbranches. a receiver operatively connected in the other of saidbranches, a multiple switch maintaining said transmitter branch normallyopen and said receiver branch normally closed, means whereby said switchupon operating closes said transmitter branch and opens said receiverbranch on both sides of said receiver, a normally open local circuit forsaid receiver inductively related to said transmitter, and means wherebysaid multiple switch when operated closes said local circuit.

4. In a telephone system, a metallic line circuit, abridge across saidcircuit, said bridge including a condenser and a hook switch,connections between the same including two parallel branches, a windingof an qinduction coil in one of said branches, a transmitter inductivelyassociated with said winding, a receiver connected in the other of saidbranches, a multiple switch maintaining said receiver branch normallyclosed and said transmitter branch normally open, means whereby saidswitch upon operating closes said transmitter branch' and opens saidreceiver branch on both sides of said receiver, and a tertiary windingfor said inductioncoil, said tertiary winding being included in anormally open local circuit in said receiver, said local circuit adaptedto be closed by the operation of said multiple switch.

Signed by me at Chicago, Cook county. Illinois, this 5 day of March,1913.

WILLIAM A. FRICKE.

Witnesses:

ARTHUR J. RAY, EDWARD D. Rims.

